It is known that repeated charging/discharging of lead or lead alloy acid batteries results in volume growth of the anode. This arises from creep and intergranular corrosion/cracking caused by tensile stress applied by the corrosion product and results in deterioration in the performance of the battery and also reduces its service length. Intergranular corrosion is a localized attack along the grain boundaries, or immediately adjacent to grain boundaries, while the bulk of the grains remain largely unaffected.
It is therefore known that the grain structure in the lead plate affects the occurrence of intergranular corrosion. In order to suppress grain boundary corrosion, the grain size at the anode should be of medium size (often 100-200 μm). At the cathode it is more important that the material is easy to form and manufacture, and depending on manufacturing method, a smaller grain size (10-20 μm) may be preferrable. It is desirable to be able to control and modify the crystallographic structure of grains and grain boundaries during the manufacturing process of lead or lead alloy electrodes.
The lead or lead alloy plate may be manufactured to a plate lattice by a punching process or the plate may be perforated and subsequently stretched to provide a net-like structure.
Another known way to manufacture lead plates is by casting or by a continuous extrusion process. A drawback with continuous extrusion is that the width of the plate is limited by the width of the extrusion apparatus.
In patent application US 2005/0066498A1, a process for manufacturing a lead or lead alloy anode plate lattice for lead-acid batteries with controlled grain size is disclosed. A melt of lead or lead alloy is extruded to the shape of a pipe, provided with a slit and cold rolled. The grain size in the lead or lead alloy plate is controlled by controlling the temperature of the extrudate during the cold rolling. The cold rolling is performed under a temperature of about 50-230° C. below the melting point of lead or the lead alloy, and the extrudate is cold rolled with a total draft rate of about 10-90%.